Assertion (A) The total number of atoms present in a simple cubic unit cell is one.

Reason (R) Simple cubic unit cell has atoms at its corners, each of which is shared between eight adjacent unit cells.

Assertion (A) Graphite is a good conductor of electricity however diamond belongs to the category of insulators.

Reason (R) Graphite is soft in nature on the other hand diamond is very hard and brittle.

Assertion (A) Total number of octahedral voids present in unit cell of cubic close packing including the one that is present at the body centre, is four.

Reason (R) Besides the body centre there is one octahedral void present at the centre of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.

Assertion (A) The packing efficiency is maximum for the fcc structure.

Reason (R) The coordination number is 12 in fcc structures.

Assertion (A) Semiconductors are solids with conductivities in the intermediate range from $10^{-6}-10^4 \mathrm{ohm}^{-1} \mathrm{~m}^{-1}$.

Reason (R) Intermediate conductivity in semiconductor is due to partially filled valence band.